1. Technical Field
The present invention relates to a radiographic imaging device and a radiographic imaging system, and in particular, relates to a radiographic imaging device and a radiographic imaging system that carry out capturing of a radiographic image expressed by radiation that is emitted from a radiation source and passes through a subject.
2. Related Art
Radiation detectors such as FPDs (Flat Panel Detectors), in which a radiation-sensitive layer is disposed on a TFT (Thin Film Transistor) active matrix substrate and that can convert radiation such as X-rays or the like directly into digital data, and the like have been put into practice in recent years. A radiographic imaging device, that captures radiographic images expressed by irradiated radiation, is put into practice by using this radiation detector. As compared with a radiographic imaging device that uses conventional X-ray films or imaging plates, a radiographic imaging device using this radiation detector has the advantages that an image can be confirmed immediately, and through-imaging (fluorscopic imaging), which is video imaging that carries out capturing of radiographic images continuously, can also be carried out.
Various types of such radiation detectors have been proposed. For example, there are: an indirect-conversion-type radiation detector that once converts radiation into light at a scintillator of CsI:Tl, GOS (Gd2O2S:Tb), or the like, and, at sensor portions such as photodiodes or the like, converts the converted light into charges, and accumulates the charges; a direct-conversion-type radiation detector that converts radiation into charges at a semiconductor layer of amorphous selenium or the like; and the like. In the radiographic imaging device, the charges accumulated in the radiation detector are read-out as electric signals, and, after the read-out electric signals are amplified at an amplifier, the amplified signals are converted into digital data at an A/D (analog/digital) converting section.
In an indirect-conversion-type or direct-conversion-type radiation detector, there are cases in which charges become trapped in impurity potentials within the sensor portions, such as photodiodes, or within the semiconductor layer, and residual images arise.
A light calibration method is known as a technique for erasing such residual images. In the light calibration method, noise is reduced by forming the substrate of a radiation detector of a material that is light-transmissive, placing a light guide plate on the substrate side, illuminating light from the substrate side, and filling-in the impurity potentials of the respective sensor portions of the radiation detector before imaging.
For example, Japanese Patent Application Laid-Open (JP-A) No. 2008-256675 discloses a technique in which plural light sources that can emit light are disposed with respect to one surface of a planar detector that includes a conversion section in which plural pixels, that include converting elements that can convert radiation into charges, are disposed in the form of a matrix. A signal that is acquired at a predetermined cycle from the planar detector and a reference value that is set in advance are compared. On the basis of the results of comparison, light is discharged from the plural light sources with respect to the entire one surface of the planar detector.
However, in the technique of JP-A No. 2008-256675, the occurrence of residual images can be suppressed, but because light is illuminated with respect to an entire one surface of the planar detector from the light sources, there is the problem that consumption of electric power cannot be suppressed.
In recent years, portable radiographic imaging devices (hereinafter also called “electronic cassettes”) also have been put into practice. The electronic cassette incorporates therein a radiation detector, a control section including an image memory, and a power source section such as a battery or the like, and stores, in the image memory, radiographic image data that is outputted from the radiation detector. Because the electronic cassette is operated by electric power from the power source section such as a battery or the like, if the capacity of the battery is made to be large, the weight of the electronic cassette increases, the portability deteriorates, and further, the size of the device also is increased. Therefore, in electronic cassettes in particular, it is important to suppress consumption of electric power.